Conventionally, hair cosmetics focused on the prevention and the amelioration of alopecia have been developed. Since male pattern alopecia cases make up high percentage of all alopecia cases, the application of components having an antiandrogenic action has been particularly examined, and those which competitively inhibit the binding of dihydrotestosterone, which is an activated testosterone, to receptors, and those which inhibit testosterone 5 α-reductase, which is an enzyme that catalyzes the conversion of testosterone into dihydrotestosterone, have been disclosed. An example of the former includes cyproterone acetate, and examples of the latter include androstanone derivatives, bicycloheptenone derivatives, phenoxybutane derivatives, tocopherylquinone, tropolone derivatives, ubiquinone, and also, extracts from many plants including labiatae and asteraceae (for example, see Japanese Laid-open Patent Application Nos. 5-339133 and 7-330555, and Tokushima Journal of Experimental Medicine, 9, 37-59 (1962)), and extracts from mushrooms (for example, see Japanese Laid-open Patent Application No. 11-193220).
In addition, the application of the followings has been examined: those which have a stimulatory effect on the circulation in the scalp, such as 6-(1-piperidinyl)-2,4-pyrimidinediamine-3-oxide (minoxidil) (for example, see the specification of U.S. Pat. No. 4,139,619), cepharanthin, vitamin E derivatives, carpronium chloride, and urea (for example, see Japanese Laid-open Patent Application No. 7-267830); and those which have an activating effect on hair follicles including hair matrix cells, such as adenosine triphosphate, urogastrone, baicalein, pantetheine-S-sulfonate, and odd-chain fatty acid derivatives. Further, external preparations for the head in which 5-aminolevulinic acids, which are already known as herbicides, plant regulators, etc., are contained as active components, are known (for example, see Japanese Laid-open Patent Application No. 11-116446).
However, other than testosterone-dependent male pattern alopecia, alopecia is triggered by various causes such as aging, malnutrition, and stress, which is particularly popular in the modern society. For alopecia other than male pattern alopecia thus described, the effect of components having an antiandrogenic action cannot be expected, and further, among the components having the antiandrogenic action mentioned above, there are many components that might express a side effect, that show poor stability in a cosmetic base, or that show an insufficient action effect. In addition, as to components derived from natural products such as plant extracts, there are many components that are difficult to be obtained with a certain quality, and that have undesirable colors and odors to be blended into cosmetics. Further, among those reported to have a stimulatory effect on the circulation in the scalp and to have an activating effect on hair follicles, there are not many components with which a sufficient action effect can be obtained at a low concentration, and some components have problems in their stability and safety.
Conventionally known external preparations for head (hair restorers) containing 5-aminolevulinic acids as active components cannot be used stably because of the following reasons; they cause damages to hair when they are not used in accordance with the direction of their dosage and use, resulting in problems such as split ends and decrease in the number of hairs, and in addition, light shielding at the point of use is an absolute requirement. The object of the present invention is to solve problems in use of external preparations for the head containing 5-aminolevulinic acids as active components, and to provide a hair restorer with higher stability and safety, whose usage is simple, and which exhibits an excellent stimulatory effect on hair restoration against hair loss, hair thinning, split ends, hair graying, etc.
In order to solve the above-mentioned problems caused by using 5-aminolevulinic acids, the present inventor made a keen study by conducting experiments with a lot of compounds and studied intensively on the assumption that the use of 5-aminolevulinic acid in combination with other various compounds would lead to a simple usage, and the exhibition of safe and stable hair restoring effect. As a result, the present inventor has found that the problems that occurred when 5-aminolevulinic acid was used alone, such as hair removal and light shielding condition at the point of use, can be avoided by using 5-aminolevulinic acids and iron compounds in combination, and the present invention has been thus completed.